Abstract. Net ozone production rates, P(O3), were measured directly using the
Penn State Measurement of Ozone Production Sensor (MOPS) during the Study of
Houston Atmospheric Radical Precursors (SHARP, 2009). Measured P(O3)
peaked in the late morning, with values between 15 ppbv h−1 and
100 ppbv h−1, although values of 40–80 ppbv h−1 were typical for
higher ozone days. These measurements were compared against ozone production
rates calculated using measurements of hydroperoxyl (HO2), hydroxyl
(OH), and nitric oxide (NO) radicals, called "calculated P(O3)". The
same comparison was done using modeled radicals obtained from a box model
with the RACM2 mechanism, called "modeled P(O3)". Measured and
calculated P(O3) had similar peak values but the calculated P(O3)
tended to peak earlier in the morning when NO values were higher. Measured
and modeled P(O3) had a similar dependence on NO, but the modeled
P(O3) was only half the measured P(O3). The modeled P(O3) is
less than the calculated P(O3) because the modeled HO2 is less
than the measured HO2. While statistical analyses are not conclusive
regarding the comparison between MOPS measurements and the two estimation
methods, the calculated P(O3) with measured HO2 produces peak
values similar to the measured P(O3) when ozone is high. Although the
MOPS is new and more testing is required to verify its observations, the
measurements in the SHARP field campaign show the potential of this new
technique for contributing to the understanding of ozone-producing chemistry
and to the monitoring of ozone's response to future air quality regulatory
actions.